Lost one button on Defender CP rebuild

PrairieDillo

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Donor 2011, 2024
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This free defender I had rgottn a couple months back had a very hacked up CP where they had lots of old leafs mixed levered cherry switches on the leaf buttons.

I took out everthing and re-wired it and used better used parts from my other defender. I then lost the reverse button. I checked continuity down to the I/O board and everything is good.

Can you just loose one button on the Defender I/O board like that? it's very odd to me.
 
I had a Mappy board where player 1 start didn't work. Someone else fixed it and it turned out to be a resistor fairly close to the input in a resistor pack that had failed.
 
I have another one that wasn't working with missing buttons also. I swapped in this I/O board and everything worked till now. HMMMM
 
Every time I've lost a single button on Defender it's been due to a bad connection at the I/O board. Pull the board, reflow the solder on the header pins and make sure the pins aren't corroded. You can test the board by removing the harness, putting the game into the switch test in diags, and ground each pin individually and see if the game reports it.
 
With Williams games there are usually two ways that you can lose buttons.
1) There is a break in the continuity between the input pin on the I/O card and ground. This can be caused by one or more of:
a) switch is bad or dirty
b) ground connection is broken
c) wire to I/O board is broken
d) bad connection (connector/solder) at switch or the I/O connector
2) The PIA on the I/O board loses a channel.

To test for (1), unplug the I/O connector and check continuity from the connector through the switch and back to ground. I usually insert a small wire into the appropriate connector pins and check the continuity while pressing the button.

If there is continuity, then I will place the game into switch test mode and manually ground the pins with a jumper cable and watch the display. If it does not show the pin activating the corresponding switch. I'll break out the logic probe and make sure the signal is flowing correctly through the input circuit. Many times it is one of the 4049 chips that has gone bad. It is rare when the PAI chip goes bad that you don't lose more than 1 channel (usually all of them).

In order of likelihood with only one switch:
about 80% - ground interruption (dirty contacts, broken wire, etc.)
about 15% - input chip on I/O card
about 5% - PIA chip on I/O card.

ken
 
thanks for the help guys... something to test when I get home.

UPDATE - I polished the connector pins... and reflowed the solder... now it works!

Thanks guys.
 
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